From BatteryUniversity.com (with comments from me in
BLUE):
The Lithium Polymer battery
The Li-polymer differentiates itself from other battery systems in the type of electrolyte used. The original design, dating back to the 1970s, uses a dry solid polymer electrolyte. This electrolyte resembles a plastic-like film that does not conduct electricity but allows an exchange of ions (electrically charged atoms or groups of atoms). The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.
The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry. There is no danger of flammability because no liquid or gelled electrolyte is used. With a cell thickness measuring as little as one millimeter (0.039 inches), equipment designers are left to their own imagination in terms of form, shape and size.
Unfortunately, the dry Li-polymer suffers from poor conductivity. Internal resistance is too high and cannot deliver the current bursts needed for modern communication devices and spinning up the hard drives of mobile computing equipment. Heating the cell to 60°C (140°F) and higher increases the conductivity but this requirement is unsuitable for portable applications.
To make a small Li-polymer battery conductive, some gelled electrolyte has been added. Most of the commercial Li-polymer batteries used today for mobile phones are a hybrid and contain gelled electrolyte. The correct term for this system is Lithium Ion Polymer. For promotional reasons, most battery manufacturers mark the battery simply as Li-polymer. Since the hybrid lithium polymer is the only functioning polymer battery for portable use today, we will focus on this chemistry.
With gelled electrolyte added, what then is the difference between classic Li‑ion and Li‑ion polymer? Although the characteristics and performance of the two systems are very similar, the Li‑ion polymer is unique in that solid electrolyte replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity.
Technical difficulties and delays in volume manufacturing have deferred the introduction of the Li‑ion polymer battery. In addition, the promised superiority of the Li‑ion polymer has not yet been realized. No improvements in capacity gains are achieved — in fact, the capacity is slightly less than that of the standard Li‑ion battery. For the present, there is no cost advantage. The major reason for switching to the Li-ion polymer is form factor. It allows wafer-thin geometries, a style that is demanded by the highly competitive mobile phone industry.
[TD="colspan: 2"][TABLE="width: 100%"]
[TR]
[/TD]
[/TR]
[TR]
[TD="width: 482, bgcolor: #e6e6e6, colspan: 2"]
Advantages and Limitations of Li-ion Polymer Batteries
[/TD]
[/TR]
[TR]
[TD="width: 482, colspan: 2"][TABLE="width: 100%"]
[TR]
[TD]
[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR]
[TD="width: 65"]
Advantages
[/TD]
[TD="width: 417"]
Very low profile — batteries that resemble the profile of a credit card are feasible.
Flexible form factor — manufacturers are not bound by standard cell formats. With high volume, any reasonable size can be produced economically.
Light weight – gelled rather than liquid electrolytes enable simplified packaging, in some cases eliminating the metal shell.
Improved safety — more resistant to overcharge; less chance for electrolyte leakage.
[/TD]
[/TR]
[TR]
[TD="width: 65, bgcolor: #f3f3f3"]
Limitations
[/TD]
[TD="width: 417, bgcolor: #f3f3f3"]
Lower energy density and decreased cycle count compared to Li-ion — potential for improvements exist.
Expensive to manufacture — once mass-produced, the Li-ion polymer has the potential for lower cost. Reduced control circuit offsets higher manufacturing costs.
[/TD]
[/TR]
[TR]
[TD="colspan: 2"][TABLE="width: 100%"]
[TR]
[TD]
[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[/TABLE]
And the chart below shows the operating temperature ranges for the LIPO battery at between 0 & 60C, which is 32 to 140F. They essentially stop working at below freezing and at above 60C or 140F, they are damaged potentially to a point of complete failure. It should also be noted that exposure to temperatures of over 113F (45C) begins to have an effect on the usable life of the battery accelerating the slow decent to death. By manufacturing standards, a battery of this type which no longer can maintain a charge of 80% (in an earlier thread I had mentioned some manufacturers specify 70%), of the original battery's charge capacity is considered at end of life.
[TD="colspan: 7"][TABLE="width: 100%"]
[TR]
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #e6e6e6"][/TD]
[TD="width: 12%, bgcolor: #e6e6e6"]
NiCd
[/TD]
[TD="width: 12%, bgcolor: #e6e6e6"]
NiMH
[/TD]
[TD="width: 11%, bgcolor: #e6e6e6"]
Lead Acid
[/TD]
[TD="width: 12%, bgcolor: #e6e6e6"]
Li-ion
[/TD]
[TD="width: 12%, bgcolor: #e6e6e6"]
Li-ion polymer
[/TD]
[TD="width: 14%, bgcolor: #e6e6e6"]
Reusable
Alkaline
[/TD]
[/TR]
[TR]
[TD="colspan: 7"][TABLE="width: 100%"]
[TR]
[TD]
[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Gravimetric Energy Density(Wh/kg)
[/TD]
[TD="width: 12%"]45-80
[/TD]
[TD="width: 12%"]60-120
[/TD]
[TD="width: 11%"]30-50
[/TD]
[TD="width: 12%"]110-160
[/TD]
[TD="width: 12%"]100-130
[/TD]
[TD="width: 14%"]80 (initial)
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Internal Resistance
(includes peripheral circuits) in mΩ
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]100 to 200[SUP]1[/SUP]
6V pack
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]200 to 300[SUP]1[/SUP]
6V pack
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]<100[SUP]1[/SUP]
12V pack
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]150 to 250[SUP]1[/SUP]
7.2V pack
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]200 to 300[SUP]1[/SUP]
7.2V pack
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]200 to 2000[SUP]1[/SUP]
6V pack
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Cycle Life (to 80% of initial capacity)
[/TD]
[TD="width: 12%"]1500[SUP]2[/SUP]
[/TD]
[TD="width: 12%"]300 to 500[SUP]2,3[/SUP]
[/TD]
[TD="width: 11%"]200 to
300[SUP]2[/SUP]
[/TD]
[TD="width: 12%"]500 to 1000[SUP]3[/SUP]
[/TD]
[TD="width: 12%"]300 to
500
[/TD]
[TD="width: 14%"]50[SUP]3[/SUP]
(to 50%)
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Fast Charge Time
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]1h typical
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]2-4h
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]8-16h
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]2-4h
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]2-4h
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]2-3h
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Overcharge Tolerance
[/TD]
[TD="width: 12%"]moderate
[/TD]
[TD="width: 12%"]low
[/TD]
[TD="width: 11%"]high
[/TD]
[TD="width: 12%"]very low
[/TD]
[TD="width: 12%"]low
[/TD]
[TD="width: 14%"]moderate
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Self-discharge / Month (room temperature)
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]20%[SUP]4[/SUP]
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]30%[SUP]4[/SUP]
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]5%
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]10%[SUP]5[/SUP]
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]~10%[SUP]5[/SUP]
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]0.3%
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Cell Voltage(nominal)
[/TD]
[TD="width: 12%"]1.25V[SUP]6[/SUP]
[/TD]
[TD="width: 12%"]1.25V[SUP]6[/SUP]
[/TD]
[TD="width: 11%"]2V
[/TD]
[TD="width: 12%"]3.6V
[/TD]
[TD="width: 12%"]3.6V
[/TD]
[TD="width: 14%"]1.5V
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Load Current
- peak
- best result
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]20C
1C
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]5C
0.5C or lower
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]5C[SUP]7 [/SUP]
0.2C
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]>2C
1C or lower
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]>2C
1C or lower
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]0.5C
0.2C or lower
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Operating Temperature(discharge only)
[/TD]
[TD="width: 12%"]-40 to
60°C
[/TD]
[TD="width: 12%"]-20 to
60°C
[/TD]
[TD="width: 11%"]-20 to
60°C
[/TD]
[TD="width: 12%"]-20 to
60°C
[/TD]
[TD="width: 12%"]0 to
60°C
[/TD]
[TD="width: 14%"]0 to
65°C
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Maintenance Requirement
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]30 to 60 days
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]60 to 90 days
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]3 to 6 months[SUP]9[/SUP]
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]not req.
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]not req.
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]not req.
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Typical Battery Cost
(US$, reference only)
[/TD]
[TD="width: 12%"]$50
(7.2V)
[/TD]
[TD="width: 12%"]$60
(7.2V)
[/TD]
[TD="width: 11%"]$25
(6V)
[/TD]
[TD="width: 12%"]$100
(7.2V)
[/TD]
[TD="width: 12%"]$100
(7.2V)
[/TD]
[TD="width: 14%"]$5
(9V)
[/TD]
[/TR]
[TR]
[TD="width: 23%, bgcolor: #f3f3f3"]
Cost per Cycle(US$)[SUP]11[/SUP]
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]$0.04
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]$0.12
[/TD]
[TD="width: 11%, bgcolor: #f3f3f3"]$0.10
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]$0.14
[/TD]
[TD="width: 12%, bgcolor: #f3f3f3"]$0.29
[/TD]
[TD="width: 14%, bgcolor: #f3f3f3"]$0.10-0.50
[/TD]
[/TR]
[TR]
[TD="width: 23%"]
Commercial use since
[/TD]
[TD="width: 12%"]1950
[/TD]
[TD="width: 12%"]1990
[/TD]
[TD="width: 11%"]1970
[/TD]
[TD="width: 12%"]1991
[/TD]
[TD="width: 12%"]1999
[/TD]
[TD="width: 14%"]1992
[/TD]
[/TR]
[/TABLE]
As far as component damage, the phone itself has temperature sensors (the numbers you are reading), and will make necessary adustments to clock rate by reducing it to use less power thereby producing less heat, killing certain applications running, and even doing either a soft or hard reboot to prevent damage to the components.
You should protect the phone from excess heat in addition to what it is already producing, so don't leave it in the trunk or inside of a closed car in the sun, and whatever else you need to do to further protect it from the heat it's building up inside being enhanced by ambient temperatures outside. Remember, this IS a computer, but it doesn't have an active cooling fan like almost all laptops and nearly all desktop computers. Without a way to more aggressively move heat away, its only defense is to shut down services, radios, charging circuitry, and eventually itself.